This invention relates to moisture activated windshield wiper controls. Controls of this type typically include an optical sensor aimed at a vehicle windshield and electronic circuitry for processing signals from the optical sensor to detect the presence of water droplets on the windshield. The output of the processing circuit controls the wiper motor at a variable speed governed by the amount of water on the windshield. Controls of this type are shown in Teder, U.S. Pat. No. 5,059,877, the disclosure of which is incorporated by reference.
Prior art moisture activated wiper controls use two separate modules to perform the rain detecting and signal processing functions. The first module contains the optical elements for emitting light toward the windshield and collecting the reflected light. This module is mounted on the windshield in the vehicle interior, usually behind a rear view mirror. Since the alignment of the light emitters and collectors is critical to successful moisture detection, the first module has been relatively bulky to assure proper alignment of the optical elements. As a result, there has been no room in the first module for the associated processing Circuitry which creates the wiper motor control signal. Accordingly, the electronic circuitry for processing signals from the light collectors has been housed in a separate, second module. Again due to the size of the first module, the second module has been located remote from the first module, usually somewhere in the vehicle dash. This dual module design with the remote location of the processing circuitry module complicates installation, service and repair, adding to the cost of the system. It also requires wiring the two modules together, further adding to the overall cost.